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24 Cards in this Set
- Front
- Back
Who planted pea plants and observed their physical traits?
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Gregor Mendel
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Gene
Allele |
Gene = genetic coding for a specific trait
Allele = variation of that trait |
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What terms did Mendel use for genes and alleles?
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Genes = characters
Alleles = traits |
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In Mendel's experiments, what was the gene and what was the allele?
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Gene = flower color
Allele = purple or white For each gene there was 2 alleles |
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Genotype vs. phenotype
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Genotype = genetic make up
Phenotype = physical (appearance) and physiological (functioning) characteristics; determined by the genotype |
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Carpel
What are they? Which are they? |
Female structures of a flower
1) Stigma = a receptive surface for pollen 2) Style = column through which the pollen travels to the ovary 3) Ovary = when fertilizes is the fruit 4) Ovule = egg, when fertilizes is the seed |
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Stamen
What are they? Which are they? |
Male structures of a flower
1) Anther = pollen bearing part 2) Filament = arm that supports the anther |
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What is a parental generation called, and what is a descendant generation called?
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Parental = P
Descendant = F1, F2, F3, etc... (filial = son) |
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Mendel's initial experiment and results
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Experiment:
P generation purple flowers pollinated with the pollen of the white flowers Results: Entire F1 generation grew purple flowers |
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Selfing
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Pollinating flowers with their own pollen
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Mendel's second experiment and results
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Experiment:
He selfed the F1 generation Results: 3:1 purple to white |
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What did Mendel conclude from his second experiment?
4 |
1) The purple flowers had the white trait, but it was hidden by the purple trait
2) There are recessive and dominant traits 3) Organisms inherit 2 copies of a gene, 1 from each parent 4) dominant and recessive are variants of the same gene |
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Monohybrid cross
When did Mendel do this? |
When looking at 1 gene
Conducted for the Law of Segregation |
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Law of Segregation
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• Mendel's version of homologous pairs in meiosis
• The 2 alleles for a gene separate during meiosis and are rejoined at random at fertilization • 1 allele is from each parent |
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What are dominant and recessive alleles are represented by?
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Dominant = capital letter; ex. G for green pea pod color
Recessive = the same letter, lowercase; ex. g for yellow pea pod color |
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Homozygous
Homozygous dominant Homozygous recessive Heterozygous |
Homozygous = 2 identical alleles
Homozygous dominant = 2 dominant alleles; ex. GG Homozygous recessive = 2 recessive alleles; ex. gg Heterozygous = 1 dominant, 1 dominant allele; ex. Gg |
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Test cross
Why it's used (2) What is done (1) Possible results (2) |
• Used when an individual is expressing a dominant phenotype, but the genotype is unknown
• determines if individual is homozygous dominant or heterozygous • mate the individual with a homozygous recessive Results: 1) homozygous dominant = all offspring will be heterozygous and exhibit the dominant trait 2) heterozygous = 1/2 the offspring will be heterozygous and exhibit the dominant trait, and 1/2 will be homozygous recessive and exhibit the recessive trait |
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Dihybrid cross
When did Mendel do this? |
When looking at 2 genes
Conducted for the Law of Independent Assortment |
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Law of Independent Assortment
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1) Since chromosomes randomly align during metaphase I on the metaphase plate, they segregate independently of one another during anaphase
2) alleles that are paired in one generation do not necessarily get inherited as a pair |
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When does the Law of Independent Assortment not apply?
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When genes are closely located on the same chromosome because these genes travel together during anaphase of meiosis
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What phenotype ratio did Mendel expect to see in his dihybrid cross, and what did he actually see?
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He expected 3:1 → would imply that pairs of alleles get passed on together
Actually saw 9:3:3:1 → illustrates the Law of Independent Assortment |
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Incomplete dominance
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• heterozygote appears a blend of the 2 alleles
• this is not due to blending inheritance, but rather due to failure of dominance |
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Co-dominance
Example |
• No single allele is dominant, so the heterozygote shows some aspect of both alleles
• Ex. human blood type |
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Polygenic inheritance
2 types |
1) Polygenic = many genes controlling a trait
2) Multifactorial = many factors controlling a trait, ex. environment |